This invention relates to dustless, free-flowing ultraviolet absorbing compositions for use in polyolefins. More particularly this invention relates to dustless nickel amine complexes of 2,2'-thiobis(4-alkylphenols) containing an effective amount of a low molecular weight polyethylene.
As is well-known, polyolefins are subject to degradation on prolonged exposure to ultraviolet light. It is also well-known that polyolefins can be stabilized against the deteriorative effects of ultraviolet light by incorporating therein a nickel amine complex of a 2,2'-thiobis(4-alkylphenol), as disclosed by Foster in U.S. Pat. Nos. 3,215,717 and 3,313,770 and Stretanski and Hoffman in U.S. Pat. No. 3,816,492. The nickel n-butylamine complex of 2,2'-thiobis(4-t -octylphenol), described in Example 8 of said Foster patents, is a commercially available member of this class of stabilizers.
The nickel amine complexes of 2,2'-thiobis(4-alkyl-phenol), particularly the nickel n-butylamine complex, tend inherently to be very dusty, consequently contaminating the working area with nickel and creating a hazard for workers.
The stabilizing value of these ultraviolet absorbing compounds is so great that they are widely used despite the serious dusting problem. Various attempts have been made in the past to overcome these difficulties, but such have not been completely successful and difficulties are still present. In some instances, where attempts have been made to overcome dustiness by incorporating therein small amounts of a mineral oil or plasticizer, the products were found to be sticky, not free-flowing, and to tend to cake. This makes the material difficult to process.
Thus, there is a need for dustless nickel amine complexes of 2,2'-thiobis(4-alkylphenols) which are also free-flowing and non-sticky, and which can be easily and uniformly incorporated in polyolefins by conventional blending means.